The prior art includes sliding windows with sashes which slide between opened and closed positions in parallel tracks. Generally, such windows include two sashes which slide in parallel, offset tracks. Weatherstripping seals the spaces between the sashes and between the sashes and tracks. Although traditional window assemblies (including sashes and tracks) have been made of wood, modern manufacturing techniques and materials have made it possible to manufacture these components from metal or plastics, or a combination, and such combined materials have thermal, esthetic and economic advantages.
Additionally, there have been windows of the sliding type which have mechanisms allowing the window sash to pivot about an axis so that the sash may be washed on both sides from within the building in which it is installed. Windows of this type have been both vertically double hung windows and horizontally sliding windows. The pivot mechanisms have included movable pins mounted on one edge of the sash which may be extended upward and downward to engage holes in the track and to form the axis about which the sash may be pivoted. At the opposite vertical edge are releasable track engaging members which may be withdrawn from the track to allow the sash to pivot.
Although such windows have worked, special steps have been required to maintain the sash steady when it is pivoted out of its usual sliding plane. For example, U.S. Pat. No. 4,222,201 shows such a window assembly, and it requires that spring loaded pins be released so that the springs push the pins into circular passages formed in the tracks. Then the sash may be pivoted. When window cleaning is complete, the pins must be retracted against the spring bias to free the pins from the circular passages, and locknuts must be secured to hold the pins in the retracted position for ordinary sliding. Not only does this mechanism require moving parts which may over time corrode or bind, but the pivoting procedure is complicated, and there may be problems with the sash not being adequately stable when pivoted open.